1. Field of This Invention
This invention relates to a process for the production of a monohaloacetylhalide by the halogenation of a ketene in the liquid phase. This invention particularly relates to the halogenation of a ketene in the presence of a solvent, which impedes or prevents the formation of polyhaloacylhalides and keeps the formation of acylhalides to a minimum.
2. Prior Art
The halogenation of ketene in the liquid phase is known. However the known methods for carrying out such conversion lead to the formation of monohaloacetylhalides which are contaminated to a considerable degree with dihaloacetylhalides and polyhalogenated by-products. In the known processes, solvents such as alkyl-acetates (Brit. Pat. No. 782,773), SO.sub.2 (U.S. Pat. No. 2,889,365), alicyclic carbonates, alkoxyalkylesters, glycolesters (Germ. OS No. 2,247,764), sulfones (U.S. Pat. No. 3,882,173), phosphate esters (U.S. Pat. No. 3,883,589) or lactones (Germ. OS No. 2,247,765) have been used. Most of such solvents have the common disadvantage that their use leads to the formation of a considerable quantity of dihaloacetylhalide along with the desirable monohaloacetylhalide product. Such dihalogen derivataives have no commercial value and, moreover, their separation from the monohalogen derivatives is too expensive and time consuming. Thus, for example, dichloroacetylchloride has a boiling point of almost 107.degree. C., while monochloroacetylchloride has a boiling point of 105.degree. C. Because the boiling points are very close together, it is difficult to separate these two compounds. An expensive and unprofitable separation must follow the halogenation process whenever the halogenation is carried out in the known solvents used for this purpose. When phosphate esters lactones are used as solvents, only small quantities of undesirable by-product are obtained.